Solar energy collecting system

Abstract

In a solar energy collecting system which comprises a primary closed circuit including a solar energy collector, a heat exchanger, a carrier fluid receiver tank, and a circulating pump and a secondary closed circuit including a utilization means and engaged with the primary closed circuit through the heat exchanger, a heat carrier used in the primary closed circuit is a fluid capable of evaporating at low temperature under low pressure and the control of the primary closed circuit is performed according to a surface temperature of the solar energy collector, a temperature of the carrier emanating from the collector and/or a pressure of the carrier in the primary closed circuit.

What is claimed is: 
     
       1. A solar energy collecting system utilizing latent heat transfer, comprising a primary closed circuit including, in series, a solar energy collector, a heat exchanger, a carrier receiver tank and a first circulating pump for circulating a heat carrier through said primary closed circuit, said carrier capable of evaporating at a low temperature under a low pressure, and a first control means responsive to surface temperatures of said solar energy collector, the temperature of said heat carrier emanating from said collector and a pressure in said heat exchanger and being operable to output a control signal to control the operation of said pump and the flow of fluid through a bypass circuit connected across said pump by opening and closing a control valve thereof to maintain the temperature of said carrier emanating from said collector at substantially a constant value, a secondary closed circuit including, in series, said heat exchanger, a utilization means, a second circulating pump for circulating water through said secondary circuit and a second control means responsive to the temperature of said water in said secondary circuit to maintain the temperature thereof at substantially a constant value. 
     
     
       2. A solar energy collecting system claimed in claim 1, wherein said first control means comprises a first means responsive to the temperature of said heat carrier emanating from said collector in said primary closed circuit to regulate an amount of said heat carrier to be supplied to said collector to thereby maintain said carrier temperature substantially constant, and a second means responsive to the temperature of said collector and to the pressure in said heat exchanger to control the starting and stopping operation of said first circulating pump. 
     
     
       3. A solar energy collecting system claimed in claim 2, wherein said first means includes said control valve connected in parallel to said first circulating pump and a carrier temperature detector having a set value, said carrier temperature detector being adapted to provide a valve open signal to said control valve when the temperature of said carrier emanating from said collector becomes higher than said set value and provide a valve close signal to said control valve when the temperature of said carrier emanating from said collector becomes lower than said set value. 
     
     
       4. A solar energy collecting system claimed in claim 3, wherein said second means comprises a surface temperature detector having a set value for detecting the temperature of a surface of said collector, said set value of said surface temperature detector being set higher than said set value of said carrier temperature detector, said surface temperature detector being adapted to provide a pump start signal to said pump when the surface temperature becomes higher than said set value, a pressure detector having a set value for detecting a pressure of said carrier in said heat exchanger, said pressure detector being adapted to provide a pump stop signal to said pump when the pressure of said carrier in said heat exchanger becomes higher than said set value thereof, said carrier temperature detector being adapted to provide a pump stop signal when said control valve is fully opened and the temperature of said carrier emanating from said collector becomes lower than said set value thereof. 
     
     
       5. A solar energy collecting system claimed in claim 4, wherein said first means further comprises a delay means connected between said carrier temperature detector and said control valve, said delay means being adapted to make said control valve insensitive for a predetermined time during the starting up of said system, during which the temperature of said carrier may vary abruptly. 
     
     
       6. A solar energy collecting system claimed in claim 3, wherein said first means further comprises a delay means connected between said carrier temperature detector and said control valve, said delay means being adapted to make said control valve insensitive for a predetermined time during the starting up of said system, during which the temperature of said carrier may vary abruptly. 
     
     
       7. A solar energy collecting system claimed in claims 3, 4, 5, or 6, wherein said second control means comprises a first water temperature detector for detecting the temperature of said water emanating from said heat exchanger, said first water temperature detector having a set value lower than said set value of said carrier temperature detector of said first control means and being adapted to provide a pump start signal to said pump when the water temperature becomes higher than said set value thereof. 
     
     
       8. A solar energy collecting system claimed in claim 7, further comprising an auxiliary heat source connected in parallel to said heat exchanger to provide an additional heat to said water when the water temperature is lower than said set value of said first water temperature detector. 
     
     
       9. A solar energy collecting system claimed in claim 7, wherein said heat carrier is carbonfluorohalide. 
     
     
       10. A solar energy collecting system claimed in claim 8, further comprising a second water temperature detector and wherein an amount of heat to be supplied by said auxiliary heat source is controlled by said second water temperature detector such that the heat to be supplied to said utilization means is maintained substantially constant. 
     
     
       11. A solar energy collecting system claimed in claim 8, wherein said heat carrier is carbonfluorohalide. 
     
     
       12. A solar energy collecting system claimed in claim 10, wherein said heat carrier is carbonfluorohalide. 
     
     
       13. A solar energy collecting system claimed in any of claims 1, 2, 3, 4, 5 or 6, wherein said heat carrier is carbonfluorohalide. 
     
     
       14. A solar energy collecting system claimed in claim 13, wherein said heat carrier is trichloro-trifluoroethane.